1. Field of the Invention
This invention relates to a polarizing device in which unmagnetized permanent magnets arranged on the peripheral surface of a rotor are magnetized to form magnetic poles in turn.
2. Description of the Related Art
Previously, in magnetic poles of a permanent magnet rotor using the permanent magnet as the magnetic pole of the rotor, there are a case where the magnetic pole is assembled to the rotor after being polarized, and a case where the unmagnetized magnetic pole that has not magnetized yet is polarized and magnetized after being assembled to the rotor.
However, in the case where the magnetic pole is previously polarized and is assembled to the rotor, a strong suction force acts and the assembly work becomes difficult, and therefore, in a large-sized rotor, the case where the magnetic pole is polarized after being assembled is general.
As a conventional polarizing device of a permanent magnet rotor of this kind, for example, as shown in Japanese Patent Application Laid-Open No. 9-163692 which is not shown in the figure, a device is disclosed, where the polarizing iron core is arranged around the rotor and in the meantime, a coil is wound at a position respectively corresponding to each unmagnetized permanent magnet of the rotor of this polarizing iron core, and by letting the current flow in each of these coils, respectively so that the directions of the flow of the adjacent fellow coils may be different, each unmagnetized permanent magnet is magnetized and polarized to a magnetic pole of N-pole or S-pole alternately.
However, in the case of the described polarizing device of a permanent magnet rotor, the device becomes large-sized since the polarizing iron core is arranged around the rotor, and therefore, for example, in Japanese Patent Application Laid-Open No. 10-336976, a method is disclosed, where at a position corresponding to either of the respective unmagnetized permanent magnets of the rotor, a polarizing iron core of one pole on which a coil is wound is arranged and polarized, and after that, by relatively moving the rotor or the polarizing iron core by a pitch of the unmagnetized permanent magnet while switching in turn the direction of the current flowing in the coil, each unmagnetized permanent magnet is magnetized one by one in turn, and is alternately polarized to N-pole or S-pole, and consequently, miniaturization is achieved.
The conventional polarizing device of a permanent magnet rotor achieves the miniaturization as a device, as described above, in such a way that the polarizing iron core for one pole on which a coil is wound is magnetized while switching the direction of the current flowing in the coil in turn and corresponding to each unmagnetized permanent magnet and is polarized to N-pole or S-pole, and therefore, as shown in FIG. 5, in the case where the magnetic flux 3 is generated by the current flowing in the coil 2 wound on the polarizing iron core 1 and for example, the corresponding unmagnetized permanent magnet 4a is polarized to S-pole, as clear from the distribution of the magnetic flux 3 in the figure, the magnetic flux 3 passes through the respective unmagnetized permanent magnets 4b, 4c near the unmagnetized permanent magnet 4a in the opposite direction of the magnetizing direction and the polarization is performed in the opposite direction of the direction in which the magnetizing should be performed, and therefore, in the case where the polarizing is normally performed in the desired direction at a position corresponding to the polarizing iron core 1, the polarizing in the reverse direction must be demagnetized and therefore, it is necessary to change the current flowing in the coil 2 each time, and there has been such a problem that the control of the current becomes difficult.
Furthermore, in the case where the unmagnetized permanent magnet is a rare earth magnet, the demagnetizing is difficult and the re-magnetizing needs a considerably strong magnetic field when compared with the unmagnetized one, and there has been such a problem that the current supplying unit becomes large-sized.
This invention is made to solve the described problems, and it is an object to provide a polarizing device of a permanent magnet rotor in which the effect of the opposing magnetic field is eliminated and the control of the current is easy.
According to a first aspect of the invention, there is provided a polarizing device for a permanent magnet rotor, comprising: a polarizing iron core arranged facing to a specified number of permanent magnets among a plurality of unmagnetized permanent magnets arranged at specified intervals in the circumferential direction on the peripheral surface of a rotor; a first coil wound at a position facing to a desired permanent magnet of the polarizing iron core; a pair of second coils each of which is arranged having a specified interval on the basis of the first coil in the circumferential direction on the polarizing iron core and whose direction of the flowing current is different from that of the first coil; and a power source for supplying the current to the first and second coils, wherein either of the permanent magnet and first coil is relatively moved and each permanent magnet is magnetized to form a magnetic pole in turn by the current fed from the power source.
According to a second aspect of the invention, there is provided the polarizing device for a permanent magnet rotor according to the first aspect, wherein each second coil is arranged having an interval corresponding to at least three permanent magnets with the first coil.
According to a third aspect of the invention, there is provided the polarizing device for a permanent magnet rotor according to the first aspect, wherein the second coils are wound in the direction different from that of the first coil.
According to a fourth aspect of the invention, there is provided the polarizing device for a permanent magnet rotor according to the third aspect, wherein the second coils are wound by a number of windings of half the number of windings of the first coil or less.
Furthermore, according to a fifth aspect of the invention, there is provided the polarizing device for a permanent magnet rotor according to the first aspect, wherein a notch part for expanding the clearance with the permanent magnet is formed near both sides of the first coil of the polarizing iron core.
Furthermore, according to a sixth aspect of the invention, there is provided the polarizing device for a permanent magnet rotor according to the first aspect, wherein the permanent magnet is relatively moved by rotating the rotor.